1. Field of the Invention
The present invention relates to the physical format of a rewritable type optical disc using a phase change medium or a magneto-optical medium, or a write-once type optical disc using a pigment based medium, and more particularly, to the physical format suitable for a large amount of data such as video data or audio data and a method of making the same.
2. Description of the Related Art
As a storage medium having a large capacity used for a computer, DVDs (digital video discs), MO (magneto-optical) discs or CDs (compact discs) are commercially manufactured as products. Also, with the wide-spread and expanding use of computers, a user""s requirements to change data stored in a storing medium such that the need for a storage medium capable of changing or writing once data is rapidly increasing.
As a rewritable type storing medium which enables a user to change data multiple times, there is a DVD-RAM (random access memory) using a phase change medium, an MO disc using an MO medium, and a CD-RW (rewritable) disc. Also, there is a CD-R using a pigment based medium as a write-once type storage medium in which a user can write data only one time. An address for recognizing the position where data is recorded is also stored in each of these storage media.
An ID (identification) portion for indicating the address is provided on the DVD-RAM or MO disc separately from a portion where user data is stored.
Also, a wobble address method using an FM (frequency) modulation is used to manage the address in the CD-RW or CD-R disc. Here, wobble means a wave type track indicating a structure that a track on a disc waves in a radial direction. That is, in the CD-RW or CD-R disc, the address is recorded by changing the frequency of the wobble (wave form) of the track. Thus, the user data and the address are recorded together along the track on the CD-RW or CD-R disc.
However, the conventional technology has the following problems. For example, since the ID portion is needed in the DVD-RAM or MO disc in addition to the area where the user data is recorded, an efficiency in use of a disc surface area is deteriorated.
Further, in the conventional technology since the structure of the disc surface is different in the areas where the user data is recorded and in the ID portion, a process to manufacture such discs is complicated. In particular, since the ID portion is arranged in a zigzag in the DVD-RAM disc, the manufacturing process is more complicated.
Another problem that arises is that since the address corresponds to the frequency of the wobble in the CD-RW or CD-R, a disc reproduction apparatus needs to read a signal (wobble) having a different frequency to read the address, requiring the structure of the reproduction apparatus to be complicated.
Yet another problem that arises with conventional technology is that since the frequency of the wobble of the track is changed according to an address value, the length of the track needed to represent the address changes according to the address value. Thus, the control of data recording is complicated.
Further, since the method of matching the address to the frequency of the wobble in conventional technology is one in which the address is stored by FM-modulating the wobble, the required C/N (carrier to noise) ratio is relatively high so that reliability in recording/reproduction is deteriorated.
Accordingly, it is an object of the present invention to provide an optical disc in which an efficiency in use of a disc surface area is high, manufacturing of discs is made easy, the structure of a disc reproducing apparatus is simplified, control of data recording on a disc is simplified, and the required C/N ratio is low, so that reliability in recording/reproduction is improved.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
The foregoing objects of the present invention are achieved by providing an optical disc having tracks for recording user data such as a rewritable type optical disc using a phase change medium or a magneto-optical medium, or a write-once type optical disc using a pigment based medium, in which a wobble portion waved in a radial direction of the optical disc and a non wobble portion which. is not waved are provided on the tracks, sub information which is data other than the user data is recorded on the tracks by using a combination of the wobble portion and the non wobble portion, a logical value of each bit is represented by a pair of the wobble portion and the non wobble portion, and the phase of wave in the wobble portion when a bit is a logic value of xe2x80x9c0xe2x80x9d and the phase of wave in the wobble portion when a bit is a logic value of xe2x80x9c1xe2x80x9d are different.
It is a further object of the present invention that the length of one of the wobble portion and the non wobble portion is different when a bit is a logical value of xe2x80x9c0xe2x80x9d and a logical value of xe2x80x9c1.xe2x80x9d
It is yet a further object of the present invention that the sub information is an address of the track.
It is yet a further object of the present invention that the difference between the phase of wave in the wobble portion in the case in which a bit is a logic value of xe2x80x9c0xe2x80x9d and the phase of wave in the wobble portion in the case in which a bit is a logic value of xe2x80x9c1xe2x80x9d is set to be about 180xc2x0.
It is yet a further object of the present invention that, at transition points from the wobble portion to the non wobble portion and from the non wobble portion to the wobble portion, the phase of wave in the wobble portion is set to a predetermined phase.
It is yet a further object of the present invention that the lengths of the wobble portion and the non wobble portion are set to integer multiples of one period of wave in the wobble portion.
It is yet a further object of the present invention that each of the tracks is divided into a plurality of zones in a radial direction of the optical disc.
It is yet a further object of the present invention that the sub information is a zone address of the zone.
It is yet a further object of the present invention that the phases of waves of the wobble portions of adjacent tracks in the zone are consistent.